Significance Statement

Thermal management systems are crucial for a lithium ion battery pack. High performance, safe operation and longer battery life can be achieved when the battery is operated within a small temperature variation around the room temperature. This demands the application of a thermal management system so as to maintain a safe temperature operation range. Air cooling is among the simplest cooling systems but drawbacks such as low thermal conductivity and low heat capacity discourages its use. This has therefore motivated the development of new liquid coolant thermal management systems for the lithium ion battery pack used mainly for vehicular propulsion.

In a recent paper published in Applied Energy, Suman Basu and colleagues presented a new coupled electrochemical thermal modelling of Lithium-ion battery pack thermal management system. Their aim was to develop an economically feasible, safe, compact and high performance thermal management system for the lithium ion battery pack mainly used in the electric vehicles.

First, the research team designed the novel liquid cooling based thermal management system for the lithium ion pack which comprised of commercially available cells in 6S5P formation (Fig. 1). The design ensured safety and compactness by thermally connecting the cells with conduction elements made of aluminum which are used to conduct the heat away. They then developed a coupled electrochemical thermal model for the battery pack and simulated it. A three-dimensional computational fluid dynamics was then developed and validated based on numerical model for the electrochemical thermal modeling of the battery pack at high accuracies. The performance of the battery pack under various arrangements and operating conditions was then investigated and reported.

They observed that the heat generation from the cells is the function of local temperature and reaction rate which had to be resolved so as to predict the thermal performance correctly. The three-dimensional electrochemical model was used to obtain a complete description of the heat generation from the battery pack system. The system also helped in validation against experimental results used to evaluate the performance of the thermal management system under various operating conditions. Thermal contact resistances at the conduction element-channel and cell-conduction element interfaces were observed to be the main hindrance to the operation of this thermal management system (Fig. 2).

Excellent agreement has been achieved between the experimental measurements and simulation predictions from the tests conducted. Application of the thermal interface material at the interfaces is seen to reduce the contact resistances and improve the heat transfer. The thermal management system is seen to cool the pack effectively even at minimal coolant flow rates. At high discharge rate and low coolant flow rate, the maximum temperature rise is kept at a small range. Therefore, this novel and compact thermal management system can work effectively under stringent conditions and is a suitable candidate for electric vehicle battery pack.

Fig 2: Temperature contours of the first set of parallel cells in the pack as a function of contact resistance at the solid-solid interfaces at 0.9 C discharge rate and 0.2 ms-1 flow velocity.

About the author

Suman Basu received his PhD from the Pennsylvania State University working in Electrochemical Engine Center with Prof. C. Y. Wang. He is working in Li-ion battery modelling and simulation project in Samsung R&D India – Bangalore. His main interests are in electrochemical energy storage system, Li-ion battery management system including thermal management and capacity fade, two-phase flow modeling and heat transfer in PEMFC. He received his bachelors and masters degree in Mechanical Engineering from Jadavpur University, Kolkata and Indian Institute of Technology, Kanpur respectively.